"Best ever" arguments generally hit a roadblock in tennis, usually about the refined modern equipment that makes wooden rackets and gut strings so dramatically obsolete. So let's stay in the present and ask this question: Is Serena Williams challenging Roger Federer as the best player of this generation? And could she soon own that distinction all by herself?

It has reached the point where even the most cynical insiders view Williams with reverence, at once startled and blown away by her utter dominance on court. That's how it was with Federer at his best, a time when so many sporting legends -- from Rod Laver to Tiger Woods -- sat courtside to grasp the full measure of his greatness.

Recent memory tends to be the sharpest, focusing on Williams' 91-4 record over the past 14 months and another astounding performance from Rafael Nadal at the French Open. Federer appears to be in gradual retreat -- certainly no shock, by any reasonable standard -- while Williams might be playing the best tennis of her life. In that sense, these two 31-year-old players seem to be headed in opposite directions. But let's take a measured, long-view approach to the argument. I think a strong case could be made for either.